15 to 20% of the population suffer from dentinal hypersensitivity, also known as tooth sensitivity. This malady is characterized by pain associated with ingestion of hot or cold foods, or sweets, or salty food, or pressure from toothbrushing. It is due to open dentinal tubules, usually near the gum line.
Tooth sensitivity is mainly caused by:                corrosion of enamel by acidic food and beverages        overzealous toothbrushing        excessively abrasive toothpastes        use of ultra abrasive prophylaxis pastes when you get your teeth cleaned at the dentist        gastric reflux—voluntary or involuntary        gum recession        bruxism        
Until recently, most treatments were palliative, and involved using toothpaste containing potassium salts, in particular 5% by weight of potassium nitrate in the US. Potassium cation raises the firing threshold of pulpal nerves.
A better approach is to use a dentinal tubule occluding agent. It is known that the average diameter of dentinal tubules in humans is about 1 micrometer (1μ). See: K. Forssell-Ahlberg et al., Acta Odon. Scand., 33, 243 (1975). In order for a particle to enter and occlude a dentinal tubule, it must have a diameter less than said tubule. Most prior art does not tabulate or graph the particle size distribution of the dentinal tubule occluding particles under consideration. Absent such information, when a particle size is mentioned, the reader should assume what is meant is average particle size.
In January, 1998 a new toothpaste, SQUIGLE® Enamel Saver® (made by SQUIGLE, inc., Narberth, Pa.) came on the market in the US. This toothpaste contains 36 weight percent of xylitol plus the surfactant system described in U.S. Pat. No. 5,496,541 (Mar. 5, 1996). Said toothpaste is free of irritating ingredients and was intended to help prevent oral maladies such as canker sores and cavities. But it was also found to treat and prevent periodontal disease (U.S. Pat. No. 5,900,230 May 4, 1999). A double blind clinical trial conducted by the US Army at Fort Sam Houston, Tex. (1999 to 2000, unpublished) confirmed the clinical efficacy of SQUIGLE® Toothpaste in the treatment and prevention of periodontal disease.
Quite unexpectedly, SQUIGLE® Enamel Saver® Toothpaste was also found to eliminate dentinal hypersensitivity in about half of all users who had this condition and used SQUIGLE® Toothpaste regularly. Since SQUIGLE® has no local anesthetics, such as potassium nitrate and/or other soluble potassium salts, its efficacy must be due to the finely divided solids present therein, such as the submicron portion of the abrasive silica and the colorant titanium dioxide, acting as dentinal tubule occluding agents, aided by the 36% xylitol and the surfactant system used in said toothpaste. For comparison, conventional toothpaste, which frequently has the same abrasive silica (average particle size=8 to 15μ) and colorant titanium dioxide (average particle size=1μ) as SQUIGLE®, does not have the ability to occlude open dentinal tubules the way SQUIGLE® Toothpaste does.
The tubule occluding effect of amorphous silica in toothpaste has been known for some time but, until now, the details and optimal formulations have been lacking. See:    M. Addy et al., Brit. Dent. J., 163, 45 (1987)    M. Addy, P. Mostafa, J. Oral Rehabilitation, 16, 35 (1989)    D. Gillam et al., J. Clin. Periodontol., 19, 197 (1992)    D. Gillam et al., J. Periodontol., 63, 7 (1992)    M. Kuroiwa et al., J. Periodontol., 65, 291 (1994)    E. Absi et al., J. Oral Rehabilitation, 22, 175 (1995)    C. Prati et al., J. Periodontol., 73, 183 (2002)    N. West et al., J. Oral Rehabilitation, 29, 167 (2002)